The evaluation of lumbar multifidus muscle function via palpation: reliability and validity of a new clinical test.

BACKGROUND CONTEXT

The lumbar multifidus muscle provides an important contribution to lumbar spine stability, and the restoration of lumbar multifidus function is a frequent goal of rehabilitation. Currently, there are no reliable and valid physical examination procedures available to assess lumbar multifidus function among patients with low back pain.

PURPOSE

To examine the inter-rater reliability and concurrent validity of the multifidus lift test (MLT) to identify lumbar multifidus dysfunction among patients with low back pain.

STUDY DESIGN/SETTING: A cross-sectional analysis of reliability and concurrent validity performed in a university outpatient research facility.

PATIENT SAMPLE

Thirty-two persons aged 18 to 60 years with current low back pain and a minimum modified Oswestry disability score of 20%. Study participants were excluded if they reported a history of lumbar spine surgery, lumbar radiculopathy, medical red flags, osteoporosis, or had recently been treated with spinal manipulation or trunk stabilization exercises.

OUTCOME MEASURES

Concurrent measures of lumbar multifidus muscle function at the L4-L5 and L5-S1 levels were obtained with the MLT (index test) and real-time ultrasound imaging (reference standard).

METHODS

The inter-rater reliability of the MLT was examined by measuring the level of agreement between two blinded examiners. Concurrent validity of the MLT was investigated by comparing clinicians' judgments with real-time ultrasound imaging measures of lumbar multifidus function.

RESULTS

Inter-rater reliability of the MLT was substantial to excellent (κ=0.75 to 0.81, p≤.01) and free from errors of bias and prevalence. When performed at L4-L5 or L5-S1, the MLT demonstrated evidence of concurrent validity through its relationship with the reference standard results at L4-L5 (rbis=0.59-0.73, p≤.01). The MLT generally failed to demonstrate a relationship with the reference standard results from the L5-S1 level.

CONCLUSIONS

Our results provide preliminary evidence supporting the reliability and validity of the MLT to assess lumbar multifidus function at the L4-L5 spinal level. Additional research examining the measurement properties and utility of this test should be undertaken before confident implementation with patients.